Council workers at Scotland’s largest local government union have voted overwhelmingly to reject the latest pay offer from employers amid the threat of bin strikes.

Unison members, including bin workers and nursery workers, voted by 86% to reject the latest pay offer from Cosla (the Convention of Scottish Local Authorities), on Tuesday.

The offer, described by Cosla as “fair and meaningful”, includes an hourly uplift of £0.67 or a 3.6% increase, whichever is higher.

Bin strikes could happen in Glasgow – Scotland’s largest city – as well as Stirling and Dumfries and Galloway, and would also have an impact on recycling centres, and Cireco, an arms-length waste management specialist company.

A letter from Cosla to Unison said: “The £0.67 increase to the hourly rate is equivalent to a £1,292 increase in annual salary for a full-time worker with a 37-hour working week.”

The offer was accepted by the GMB union, however, Unison recommended to members that they reject it.

The union, which is the largest organisation representing public sector workers, has mandates for strike action by waste workers at 13 councils, and for education and early years staff at five local authorities.

Council areas which could be subject to strike action from refuse workers include Glasgow, Inverclyde, South Lanarkshire and North Lanarkshire, as well as Fife, Midlothian, Stirling, and East Lothian.

A mandate was received in Clackmannanshire, Dumfries and Galloway, East Ayrshire, and West Lothian.

Industrial action on both refuse and education could occur at Perth and Kinross Council.

School strikes could take place at Shetland, Orkney, East Renfrewshire and Angus council areas.

The union said it “falls short of expectations” given the 25% real-terms pay cut over the past 14 years, and that “council workers in Scotland are angry their pay offer is not in line with other public service workers, many of whom have been given 5.5% pay rises”.

The union’s local government committee, made up of senior officials from across Scotland, will discuss next steps soon.

Unison Scotland local government committee chair, Colette Hunter, said: “Cosla and the Scottish Government need to understand the anger among council staff.

“They want a fair increase to stop their pay consistently falling behind, and for their wage increase to be in line with other areas of the economy. The last thing anyone wants to do is go on strike, but local government workers deserve better.

“This result must be a wake-up call and get the employers and Government to invest in local services and the staff who deliver them.”

Unison Scotland co-lead for local government, David O’Connor, said: “Councils are in crisis. They struggle to recruit because workers are expected to deliver even more with fewer staff and lower wages.

“That puts workers and the services they provide under intolerable pressure. It’s unsustainable it can’t go on.”

A Cosla spokesperson said: “We are deeply disappointed Unison have rejected our latest strong, above inflation, pay offer. This is the absolute limit of affordability for local government and exhausts all available funding from Scottish Government.

“Local government have a responsibility to ensure sustainable service delivery for communities. We are clear that increasing the value of any pay offer would have serious consequences. We remain concerned that Unison’s expectations cannot be met without further unpalatable difficult decisions.

“We are aware that communities will be concerned about the potential impact of industrial action on the most vulnerable. We would urge Unison to reconsider our strong offer which has an overall value of 4.27%.”

Cabinet secretary for finance and local government, Shona Robison, said: “While this Government respects Unison members’ decision, it is very disappointing.

“Thanks to £77.5 million of additional Scottish Government funding, the offer provides an above-inflation pay increase for all, with most workers receiving more than 4.0% and those on the lowest pay getting 5.63%. This offer is better than that made to local government workers in the rest of the UK.

“I am delighted GMB Scotland voted in favour of our fair, above-inflation offer which allows this hugely valued workforce to continue serving communities. I hope Unite members will to vote to accept.

“The Scottish Government has no formal role in pay negotiations although it will continue to work constructively with Cosla as efforts to secure a fair and affordable pay deal continue.

“Industrial action will serve no one’s interests and I would urge all parties involved to continue to work together constructively.”